An unusual mouse myeloma protein binding native DNA.

SP 104 is an IgA-kappa myeloma protein produced by a lymphoid tumour of CA F1 mice. It arose originally in mice injected intraperitoneally with cell-free extract of spleen from a dog with systemic lupus erythematosus. The monoclonal nature of the IgA was shown by characteristic appearance on immunoelectrophoresis, restriction to a single light chain type and ability to induce anti-idiotypic antiserum. This protein has antibody activity against native (double-stranded) DNA and its specificity is similar to the antibodies against DNA found in the sera of humans with SLE and NZB/NZW F1 mice. Its idiotype does not cross-react with idiotypes of other mouse myeloma proteins known to bind DNA.